Two known defects of two-cycle engines are their high fuel consumption and the significant air pollution which they produce. These two defects are linked primarily to the fact that the gases burned in the cylinder are expelled by the fresh carbureted gases coming from the crankcase through the transfer channels. These fresh gases are admitted to the cylinder while the exhaust port is open, with some of the gases escaping through this port without being burned.
Various solutions have been proposed in the past to solve this problem. They include, for example, the use of valves, as well as asymmetrical operating diagrams. Engines with fuel injected directly into the cylinder have also been proposed for this purpose.